1. Field of the Invention
The present invention relates to the field of photochemistry and, more particularly, semiconductor compositions.
2. Background of the Invention
It has recently become known that small semiconductor particles have desirable optical properties, such as nonlinearity, low light scattering, and a band-gap dependence on size. The following references disclose small metal sulfide particles in various media.
Mau et al., J. Am. Chem. Soc., 106:6537-42 (1984) reports the construction, characterization, and evaluation of a system for photocatalytic hydrogen generation. The system comprises semiconductor (CdS) crystallites embedded in a polymer (Nafion.RTM.) matrix that also contains a hydrogen-evolution catalyst (Pt). The average CdS crystal size in specified preparations was estimated to be about 20 nanometers. The optical properties of the CdS are similar to those of bulk CdS.
Yamamoto et al., Inorganica Chimica Acta, 104:L1-L3 (1985) discloses the preparation of organosols of CdS and CuS and their utilization in preparing MS-poly(acrylonitrile) composites (M=Cd, Cu). One of the uses of the organosols is said to be the preparation of composites of the metal sulfides with polymers. The composites are predicted to be useful in the manufacture of electronic devices. Yamamoto et al., J. Materials. Sci. Lett., 5:132-134 (1986) discloses the electrical conduction properties of CuS- and CdS-polymer composites prepared by using organosols of CuS and CdS.
Henglein, Ber. Bunsenges. Phy. Chem., 86:301-305 (1982) discloses the photo-degradation and fluorescence of colloidal-cadmium sulfide in aqueous solutions. Weller et al., Ber. Bunsenges. Phy. Chem., 88:649-656 (1984) discloses absorption and fluorescence of small ZnS particles. The reference discloses the preparation of colloidal ZnS particles by photo-degradation of 3 nm particles or rapid precipitation in phosphate containing solution. Electron microscopy of the ZnS and CdS particles showed that they had a mean diameter of 3 nm.
Rossetti et al., J. Chem. Phys., 83:1406-1410 (1985) discloses the synthesis of PbS crystals with a diameter of about 2.5 nanometers in low-temperature colloidal solutions. The optical and structural properties of the PbS crystals are reported.
It has been found that particles of semiconductor material can be prepared directly in a copolymer matrix. These compositions have desirable optical and mechanical properties at ambient temperature.